No exploitation reportedFix available

CVE-2020-9309

Q: Is CVE-2020-9309 actively exploited?

Active exploitation of CVE-2020-9309 has not been confirmed. Its EPSS score was 1.8% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2020-9309?

CVE-2020-9309 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2020-07-15
Fixed in2.0.0
WeaknessCWE-434

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Silverstripe CMS through 4.5 can be susceptible to script execution from malicious upload contents under allowed file extensions (for example HTML code in a TXT file). When these files are stored as protected or draft files, the MIME detection can cause browsers to execute the file contents. Uploads stored as protected or draft files are allowed by default for authorised users only, but can also be enabled through custom logic as well as modules such as silverstripe/userforms. Sites using the previously optional silverstripe/mimevalidator module can configure MIME whitelists rather than extension whitelists, and hence prevent this issue. Sites on the Common Web Platform (CWP) use this module by default, and are not affected.

Timeline

dates in UTC

2020-07-1521:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-9309?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-9309?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Silverstripe mimevalidator

Branch	Affected	Fixed in	Source
2.0	< 2.0.0	2.0.0	NVD

Silverstripe recipe

Branch	Affected	Fixed in	Source
4.x	≥ 4.0.0, < 4.6.0	4.6.0	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Silverstripe mimevalidator to 2.0.0

Advisories and patches

www.silverstripe.orgVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.18.8read 2026-10-23
NVDCVSS 2.06.8read 2026-10-23
NVDweakness (CWE)CWE-434read 2026-10-23
FIRST EPSSEPSS score1.8 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published: 2020-07-15
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2020-9309?

Is CVE-2020-9309 actively exploited?

Active exploitation of CVE-2020-9309 has not been confirmed. Its EPSS score was 1.8% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-9309?

CVE-2020-9309 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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